Gynaecology & Obstetrics The placenta secretes a hormone that paicipates in stimulation of ductal growth in the mammary gland during pregnancy. This hormone is: A Endothelial growth factor (EGF) B Human chorionic gonadotropin (HCG) C Human chorionic somatotropin (HCS) D Relaxin 💡 Explanation The placenta secretes a hormone that paicipates in stimulation of ductal growth in the mammary gland during pregnancy. This hormone is: ✓ Correct Answer: C. Human chorionic somatotropin (HCS)